a(n) = (1/2)A291405(n).

Terms

a(0) =0a(1) =1a(2) =2a(3) =4a(4) =12a(5) =26a(6) =60a(7) =145a(8) =336a(9) =796a(10) =1880a(11) =4412a(12) =10400a(13) =24488a(14) =57648a(15) =135794a(16) =319744a(17) =752908a(18) =1773016a(19) =4175032a(20) =9831472a(21) =23151400a(22) =54516976a(23) =128377380a(24) =302304640a(25) =711870368a(26) =1676321856a(27) =3947423264a(28) =9295440640a(29) =21889019712